The S1 revealed Facebook’s profit in 2011 was a staggering $1 billion, gleaned through revenues of $3.71 billion, while founder mark Zuckerberg still owns around 30% of the business.

Facebook currently has 845 million users worldwide, with more than half using the network every single day.

What surprised some was the letter from Zuckerberg at the head of the filing, in which he pretty much warned investors that Facebook wants to stick to its so-called ethos:

“Facebook was not originally created to be a company. It was built to accomplish a social mission — to make the world more open and connected.

“We think it’s important that everyone who invests in Facebook understands what this mission means to us, how we make decisions and why we do the things we do.”

He continues:

People sharing more — even if just with their close friends or families — creates a more open culture and leads to a better understanding of the lives and perspectives of others.

“We believe that this creates a greater number of stronger relationships between people, and that it helps people get exposed to a greater number of diverse perspectives.”

In terms of the integration used by TripAdvisor, basically a enhanced version of Facebook Connect, Facebook says the service illustrates how third party sites can “design more deeply integrated social experiences built around users and their friends”.

“By tapping into our rich social data, TripAdvisor connects users to their friends and shares relevant content about where their friends have traveled and where they would like to visit in the future.

“While on the TripAdvisor website, friends can discuss their travel plans and recommendations and build out personal profiles of places they have been.”

While initially it did seem to some sceptics to be just another fancy feature that people wouldn’t use, over time it appears to have started having quite a significant impact.

A TripAdvisor official says by December 2011, over 57 million people had “personalised their trip planning experience” on the site using Trip Friends.

Furthermore, these people are twice as more likely to contribute content to TripAdvisor than its other users.

No wonder Facebook likes talking up the Trip Friends integration in probably the most important documents the company has ever produced.

Kevin May is editor and a co-founder of Tnooz. He was previously editor of UK-based magazine Travolution for nearly four years and web editor of Media Week UK from 2003 to 2005.

He has also worked in regional newspapers (Essex Enquirer) and started his career in journalism at the Police Gazette at New Scotland Yard in London. He has a degree in criminology and a postgraduate diploma in magazine journalism.

Michael Dozier

TripAdvisor’s numbers are a bit misleading. Facebook gave TripAdvisor something called instant personalization, which means that if you are a Facebook user, and come to TripAdvisor, TripAdvisor can read your Facebook friends list without you logging in, match it to their own user emails, and show you things your friends have done on TripAdvisor. This is an opt-out tool, meaning they can access this data without your permission or the permission of your friends.

So in essence, anyone with a Facebook account who visits TripAdvisor via a Google or any other method is technically “personalizing their TripAdvisor experience” whether they intended to or not. My guess is that the 57MM number just means 57MM people with FB accounts visited TripAdvisor and Facebook passed over their personal data.